Microwave Dielectric Properties of Ba₄(Nd_28/3-yR_y)Ti₁₈O₅₄ (R = Eu, Dy, Ho, Er and Yb) Solid Solutions

We have investigated the formation and the microwave dielectric properties of the Ba₄(Nd_28/3-y R_y)Ti₁₈O₅₄ (R = Eu, Dy, Ho, Er and Yb) solid solutions in which R ions are substituted for Nd ions in Ba_6-3xNd_8+2xTi₁₈O₅₄ solid solutions with x=2/3. Based on the change of the volume of the unit cell, it was inferred that Eu, Dy, Ho and Er ions substituted into rhombic A1-sites, but Yb ions did smaller sites such as B-sites and C-sites after substituting A1-sites. The quality factor (Q·f) improved as the ionic radius of substituted R ions increased. In the Eu series, the best Q·f value of 10405 GHz was obtained. The temperature coefficients of the reasonant frequency (τ_f) in the Dy, Ho and Er series were improved by more than 50%, but the dielectric constant (ε_r) showed only a nominal change of about 3–4 in the vicinity of 80.